The Steinhoff case is fuelling criticism of the ECB's purchases of corporate debt as part of its stimulus programme.

Draghi said the programme's risk framework had so far served the bank extremely well.

"Running such big corporate programmes it is not unusual that losses may be happening," he told a news conference after the bank left benchmark interest rates and the terms of the asset purchase scheme unchanged.

The ECB's rules only allow it to own debt as part of its asset-buying programme, which means it might have to sell its Steinhoff holding if the bonds were converted to equity.

Draghi said the ECB had stopped buying the bonds as soon as the firm's troubles emerged, and its losses from the purchases had been "by and large exaggerated by a factor of 10."

He said policymakers were discussing the issue but "I cannot elaborate a lot about what we are going to do next."

Steinhoff International Holdings NV said on Wednesday its 2016 financial results would have to be restated. It is fighting for survival after more than $14 billion was wiped off its market value last week.

Some members of the European Parliament, academics and activists have described this part of the ECB's 2.55 trillion euros bond-buying programme as too risky both for the bank's finances and its reputation.

The ECB can only buy investment-grade debt but it does not have to sell bonds that are downgraded below that level.

(Reporting by John Stonestreet; Editing by Catherine Evans)